"We're One Organization, with One Mission --- and we're One Deep!" a military acquaintance (PM) told me in frustration. Efficiency is a fine goal when one designs a large system such as a bureaucracy. But the trade-off between efficiency and risk is a tricky business. A manager who cuts back on people, leaving no overlap between individual responsibilities, may be lucky enough to do well --- in the short run. But when somebody gets sick (randomly, or due to excess stress), when the general job mix changes, when a statistical fluctuation comes, or when a sudden crisis stretches everyone to meet new challenges ... well, you get the picture. "Efficiency" goes out the window. The staff has to juggle too many simultaneous eggs, and some fall and crack. (ambiguity deliberate!) The same happens on an individual basis, when a person signs up for just one too many extracurricular activities.

There's a concept called engineering reserve, an advance budget for the unanticipated (and unanticipatable). How big a reserve to keep depends on how risk-averse one is, as well as how serious the consequences of failure may be. An engineering reserve is like an insurance policy: one hopes never to need it.